Circuit breaker



H. S. GANOl CIRCUIT BREAKER Dec. 6, 1938.

Filed Oct. 2l, 1956 2 Sheets-Sheet 1 INVENTOR v farla. B @W XI ATTO Y WITN ESSESZ Dec. 6, 1938. H'. 5, GANO 2,139,265

C IRCUIT BREAKER Filed Oct. 21, 1956 2 Sheets-Sheet 2 ff f5 l WITNESSES: INVENTOR ATTgR Y Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE CIRCUIT BREAKER Pennsylvania y Application October 21, 1936, Serial No. 106,182

23 Claims.

AMy invention relates to circuit breakers, in general, and more particularly, to quick-acting thermostatically controlled circuit breakers suitable for use in controlling lighting and distribution feeder circuits.

My invention is a modification of the circuit breaker shown in the application of O. S. Jennings. Serial No. 712,577, led February 23, 1934 and embodies some of the features of that device.

One object of my invention is to provide an improved quick-acting thermostatically controlled circuit breaker that will be simpler and less expensive to manufacture than the previously known devices of the general type.

Another object of my invention is to provide an improved snap-acting circuit breaker that will automatically move to the open-circuit position upon the occurrence of predetermined current conditions in the controlled circuit, independently of the position of the operating handle.

Another object of my invention is to provide an improved -circuit breaker which requires a minimum number of parts.

Another object of my invention is to provide 25 an improved actuating mechanism for a circuit breaker which is, in part, pivotally supported on the bimetallic trip element of the breaker.

Another object of my invention is to provide an improved actuating mechanism for a circuit 30 breaker embodying an overcenter spring for moving the movable contact to open or closed circuit position, in which the bimetallic trip element controls the line of action of the overcenter spring.

Another object of my invention is to provide an improved actuating and tripping means for a circuit breaker together with a. simple and accurate adjusting means for adjusting the tripping characteristic of the breaker.

40 The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will best be understood from the following detailed description of a specific embodiment when read in connection with the accompanyin drawings, in which:

Figure 1 is a plan view of the circuitbreaker embodying the features of my invention;

Fig. 2 is a side elevational Yview of the circuit breaker villustrated in Fig. 1 with the contact means thereof in the closed-circuit position;

Fig. 3 is a side elevational view of the circuit (C1. zoo- 116) breaker illustrated in Fig. 1, with the'contact means thereof in the open-circuit position;

Fig. 4 is a side elevational view of the circuit breaker illustrated in Fig. 1 at an instant just prior to movement of the contact means thereof 5 to the open-circuit position in response to an overload condition;

Fig. 5 is a. perspective view of an actuating member of the circuit breaker;

Fig. 6 is a perspective view of the current- 10 responsive bimetallic ltrip element and the support carried thereby; and

Fig. 7 is a fragmentary view of a modified formr of tripping means.

Referring now to the drawings, the circuit 15 breaker illustrated therein is of the two-pole type and comprises, in general, a base, a plurality of terminals, contact means, actuating means for the contact means, a common operating member for controlling' the actuating means, and a 20 pair of current-responsive trip elements for also controlling the actuating means.

The base l for the circuit breaker is constructed of any suitable molded insulating material. Two pairs of end terminals 9, one pair for each pole of the circuit breaker, are mounted in recesses provided therefor in the base 1. The end terminals may be secured to the base in any suitable manner, as for example, by means of the threaded bolts Il, which pass through openings 3o provided therefor in the base 'l and engage in threaded openings provided in the end terminals. Each of the end terminals is provided 'with an additional threaded opening for receiving cap screws I3, by means of which the line and load conductors arev adapted to be connected to the end terminals.

Since the structure of the various elements and mechanisms for each pole of the breaker are identical, a detailed description of these elements 40 `and mechanisms for only one pole of the circuit will be given.

A stationary contact l5 is mounted in a recess provided in a common insulating plate I1, which extends across both poles of the circuit breaker. The contact I5 is connected to its corresponding end terminal by means of a conductor I9, which may be formed as an integral part of the end terminal.

Arc extinguishing means 2| of the spaced-plate 50 type are mounted in a common insulating support 23 which extends across the two poles of the breaker and is secured to the base by means of a bolt 25 and nuts 2l. The particular structure of the arc-extinguishing means is not an important part of my invention, and any suitable type of arc-extinguishing means may be used. The plates of the arc extinguisher and the support therefor are provided with recesses 29 to form a path for the movable contact.

A U-shaped main frame 3| is provided for each pole of the circuit breaker, and is mounted on a plate 33. The plate-33 and the main frame 3| are adapted to be secured to the base in any suitable manvner, as for example, by means of threaded bolts not shown. 'I'he main frame has a pair of lugs 35 struck outwardly from each leg thereof for pivotally mounting a U-shaped movable contact support 31. The ends of the legs of the U-shaped movable contact support are bifurcated, as shown in Figs. 2, 3 and 4, in order to receive the lugs 35. The lugs 35 form a pivot axis or pivot point 39 for the U-shaped movable contact support 31. A movable contact 4I is secured to the center of the bight of the U-shaped contact support 31 for cooperation with its corresponding stationary contact I5.

A current-responsive trip device in the form of a bimetallic trip element 43, has one end secured to the end terminal 9 by means of rivets 45. 'Ihe free end of the bimetallic trip element has a U-shaped support 41 secured thereto in any suitable manner. The ends of the legs of the U-shaped support 41 are bifurcated as shown at 49 (Fig. 6) for receiving a movable contact actuating member, which will now be described.

The movable contact actuating member indicated generally at 5| (Fig. 5) comprises a strip of metal bent in the form of an angle to provide legs 53 and 55. The actuating member 5| has a centrally disposed elongated slot 51 formed therein to accommodate an overcenter spring which will be hereinafter described. Offset projections 59 are formed integral with the actuating member atthe junction of the legs 53 and 55 thereof. The projections 59 are adapted to seat in the bifurcations 49 provided at the ends of the less of the U-shaped support 41. It will thus be seen that the actuating member 5| is pivotally mounted on the support 41 on an axis or point indicated at 5| in Figs. 2, 3 and 4.

An overcenter spring 63 has one end thereof secured in an opening 55 at the free end of the leg 55 of the actuating member 5|, and its other end secured to a lug 61 secured to the bight of the U-shaped movable contact support 31. A common operating means indicated generally at 69 is provided for simultaneously moving the actuating members 5| of each pole of the circuit breaker. The common actuating means comprises the U-shaped operating member 1|, the ends of the legs of which are pivotally mounted on a U-shaped support 13 between the mechanisms of the two poles by means of a pivot pin 15 tov form stops 8| for limiting movement of they operating member 1|. An insulating bar I3 is secured to the top of the bight of the operating member 1| and extends across both poles of the A handle I5 is secured adjacentl circuit breaker. the center of the insulating bar I3 to form a means whereby the operating member 1I may be manually controlled. 'Angle pieces 91 are secured to the underside of the insulating bar 93 over each pole of the circuit breaker. Each angle piece 81 has a pair of depending lugs 89 struck downwardly therefrom, and a depending hook lug 9| formed on the.forward end thereof. I'he depending lugs 89 and the hook lug 9| are adapted to engage and move the leg 53 of the actuating member 5| when the operating member 1| is moved about its pivot pin 15.

Opening movement of the movable contacts 4| is limited by means of stop brackets 93 secured to the top of the support 23. An adjusting screw 95 is threaded through a bushing 91 secured in the base 1, and passes through an opening 99 in the bimetallic trip element, and is adapted to limit downward movement of the leg 55 of the actuating member 5|, and also to adjust the trip characteristic of each pole of the circuit breaker, as will be hereinafter described.

It will be noted that the pivot points 39 of the movable contact support 31 and the pivot points 5| for the actuating member 5| are mounted substantially in the same horizontal plane and are positioned adjacent one another. The bimetallic trip element 43 is of suiiicient stiffness that in the absence of an overload such as would cause flexing of the trip element, it holds the U-shaped support 41 in fixed position, thus holding the pivot axis or point 6| for .the actuating member 5| in the xed position shown in Figs. 2 and 3 of the drawings. Under these conditions, the movement of the movable contact is controlled by the movement of the operating member 69.

The electrical connections for each pole of the breaker are identical; hence the connections for only one pole will be described. Referring to Fig. 1 of the drawings, the circuit through one pole of the breaker extends from the left-hand end terminal 9 through the bimetallic trip element 4I, through a flexible shunt conductor 98, through the movable contact 4|, through the stationary contact l5, through the conductor I9, to the opposite end terminal 9. When a current of predetermined magnitude flows through the circuit described above, it heatsthe bimetallic trip element and causes the same to flex downwardly, as shown in Fig. 4 of the drawings to eiect opening of the contact means in a manner which will be hereinafter described.

It will be noted from Figs. 2 and 4 of the drawings that the operating member 1| is disconnected from the actuating members 5| when the breaker is in the closed circuit position. As shown in Figs. 2 and 4, the hook lugs 9| carried by the bar I3 of the operating member are positioned above the upper ends of the actuating members 5I so that the actuating members`5| may be moved in a clockwise direction free of the operating member 1|. This results from the fact that the pivot axis 15 of the operating member 1| and the pivot axes 6| of the actuating members 5| are located at diilerent points. This feature renders Athe movable contacts and actuating members trip free of the operating member, so that they may be tripped to open circuit position irrespective of the position in which the operating member is held.

l Thus it is impossible to lhold the breaker closed against an overload or short circuit condition.

The operation of the circuit breaker will now be described. Let it be assumed that the circuit breaker is in the closed circuit position, as shown in Fig. 2, and it is desired to move the contacts thereof to the open circuit position. It will be noted in the position of the parts illustrated in Fig. 2, that the contacts are in the closed-circuit position and that the line of action of the overcenter spring 63 is below the pivot axis or point 39 of the movable contact supports 31. In this position the spring biases and holds the movable contacts in engagement with their corresponding stationary contacts. Ii the operating handle 85 is moved from the position shown in Fig. 2 to the position shown in Fig. 3, the following actions take place. The depending lugs 89 which are longer than the lugs 9| engage the legs 53 of the actuating members 5| and rotate the same about their pivot axis or points 6| in a 'clockwise direction. Clockwise rotation of the actuating members 5| moves the lower ends of the over-center springs 63 in an upward direction to change their line of action. As soon as the line of action oil the over-center springs 63 passes above the pivot axis or point 6|, the tension of the springs continues the movement of the actuating members 5| in a clockwise direction. At this point the lugs 9| carried by the operating member have been moved down in front of the upper ends of the actuating members 5| due to the position of the pivot with respect to the position of the pivot axes 6| of the actuating members. I'he force exerted by springs 63 now moves both the actuating members 5| and the operating member in a clockwise direction sol that no further manual operating effort is required to open the breaker. As soon as the line of action of the springs passes above the pivot axes 39 of the contact supporting arms 31, the force exerted by the springs moves these arms and the movable contacts 4I carried thereby to their open circuit position with a snap action. Lugs 32 struck inwardly from the upper ends of the frame 3| limit movement of the actuating members 5| in a clockwise direction. The parts of the breaker are now in the position shown in Fig. 3, that is, the full open position. Upward movement of the movable contacts is limited by the stop brackets 93.

If it is desired to move the contacts from the position shown in Fig. 3 to the closed-circuit position shown in Fig. 2, the operating handle is moved to the left, back to the position shown in Fig. 2. The hook lugs 9| engage the legs 53 of the actuating members 5| and move the same in a counter-clockwise direction about the pivot axis 8|. The movement of the actuating members 5| in a counter-clockwise direction shifts the lower end of the over-center springs in a downward direction to change their line of action. As soon as the line of action of the overcenter springs 63 passes below the pivot axis or points 6I, the tension of the springs acts to move the actuating members 5| in a counter-clockwise direction ahead oi' the operating member. The upper ends of the legs 53 oi the actuating members 5| engage the lugs 89 and continue movement'of the operating member 1| so that no further manual operating effort is required to close the breaker.

As soon as the line of action of the springs passes below the pivot axes 39 the tension of the spring moves the contact supporting arms 31 to closed circuit position as shown in Fig. 2 with a snap action. Downward movement of the legs 55 of the actuating members 5| is limited by the adjusting screws 95.

The automatic opening of the contact means of the circuit breaker in response to overload conditions takes place in the following manner. With the circuit breaker in the closed circuit position, as shown in Fig. 2 of the drawings, i! an overload of predetermined magnitude ln the circuit controlled by either pole of the breaker -in Fig. 4 of the drawings.

occurs, the heat produced by the current causes flexing of the corresponding bimetallic trip element 43 in a downward direction, as shown in Fig. 4. The downward movement of the free end of the bimetallic trip element 43 moves the pivot axis or point 6| in a downward direction. In the normal or unflexed position of the bimetallic trip element, the pivot axis or point 6| of the actuating member is located above the line of action of the overcenter spring 63. As soon as the ilexing of the bimetallic trip element 43 has moved the-pivot axis or point 6| below the line of action of the overcenter spring 63, the tension of the spring causes'clockwise rotation of the corresponding actuating member 5| and movement of the movable contact 4| to its open circuit position when movement of the actuating member 5| has carried the line of action of spring 63 above pivot point 39. As the actuating member 5I moves in a clockwise direction, the free end of the leg 55 thereof engages and moves the angle piec'e 81 so as to cause clockwise movement of the operating member 1| above its pivot pin 15. Movement of the operating member in a clockwise direction causes the depending lugs 89 to engage and move the leg 53 of the actuating member 5| for the opposite pole of the circuit breaker from that in which the overload occurred. Movement of the said opposite actuating member 5| in a clockwise direction shifts the line of action of the opposite overcenter spring 63 and causes opening of the contact means for said opposite pole of the breaker. It will thus be seen that an overload occurring on either pole of the breaker will cause the movable contacts of each pole to move to the open circuit position. 'I'he contact means of the contact means in response to overload on one of the poles of the circuit breaker occurs, the contact means of the pole on which the load occurred cannot be reclosed by movement of the operating handle to the closed-circuit position without iirst moving the handle to the full open circuit position, because of the fact that the lowering of the axis or point 6| and the movement of the actuating member 5| -causes the leg 53 to move outside of the hook lug 9|, as shown In order to reclose the contact means of the pole on which the overload occurred, the operating handle must rst be moved to the full open position shown in Fig. 3 of the drawingsl during lwhich movement the hook lug 9| rides over the leg 53 so that it is capable of reengaging the same upon movement of the operating member 1I to the closed circuit position. After the hook lug 9| is moved over the leg 53, the circuit breaker may be closed in the usual manner, as described above in connection with the manual operation of the device.

The trip characteristics of the bimetallic trip elements for the poles of the breaker may be individually adjusted by means of the adjusting screws 95. By trip characteristic is meant the value of overload current which will cause the opening of the contact means. It will readily be seen that elevation of the adjusting screw will reduce the amount of downward movement or flexing of the bimetallic trip element neces- .sary to move the pivot axis or point 6| below the line of action of the overcenter springs 63 to cause opening of the contact means. Hence, the breaker will open more quickly in response to overloads and will also respond to lower magnitude overloads where the adjusting screw is elevated.

Electromagnetic trip devices may be substituted if desired for the bimetallic trip elements as shown schematically in Fig. 7. The supports 4l in such case would be secured to the armatures |00 of the electromagnetic trip devices. The electromagnetic coils IOI would be connected in circuit with their corresponding contact means so as to be responsive to predetermined values of overload current.

It will thus be .seen that I have provided an improved form of a circuit breaker of the protective type which is simple, rugged and inexpensive to manufacture, yet it embodies the many safety features which are desirable or required for electrical devices of this nature.

While I have disclosed a specic embodiment of my invention, it is obvious that various changes may be made in the structure of the circuit breaker Without departing from the spirit of the invention. I desire, therefore, that my invention be limited only by the prior art and the scope of the following claims.

I claim as my invention:

1. In a circuit breaker, contact means, means for moving said contact means to an open and to a closed circuit position with a snap action, comprising a pivoted contact actuating arm, a pivoted actuating member, an overcenter spring connecting said arm and said member, manual control means for moving said actuating member t0 shift the line of action of said spring relative to the pivot points of said arm and member to effect opening or closing of said contact means. and a current-responsive trip element directly supporting one of said pivot points, movable in response to predetermined conditions to move said pivot point to shift the line of action of said spring relative to said pivot points to cause opening of said contact means.

2. In a circuit breaker, a stationary and a movable contact, means for moving said movable contact to an open and to a closed circuit position with a snap action, comprising a pivoted actuating member, an overcenter spring connecting said member and said movable contact, manual control means for moving said actuating member to shift the line of action of said spring relative to the pivot point of said member to effect opening or closing of said contact means, anda current responsive trip element movable in response to predetermined conditions to shift the position oi the pivot point of said member to change the line of action of said spring relative thereto to cause opening of said Contact means.

3. In a circuit breaker, contact means, means for moving said contact means to an open and to a closed circuit position With a snap action, comprising a movable contact actuating arm, a pivoted actuating member, an overcenter spring connecting said arm and said member, manual control means for moving said actuating member for shifting the line of action of said spring relative ,70,

to the pivot point of said member to effect opening or closing of said contact means, a thermally responsive bimetallic trip element supporting the pivot point of said member, said trip element being movable in response to predetermined conditions to shift the line of action of said spring connecting said arm and said member, manual control means for moving said actuating member to shift the line of action of said spring relative to the pivot point of said member to effect opening or closing of said contact means, and a current-responsive tripelement movable in response to predetermined current conditions in the circuit controlled by the breaker for changing the position of said pivot point relative to the line of action of said spring to open said contact means.

5. In a circuit breaker, a stationary and a movable contact, means for moving said movable contact to an open and to a closed circuit position with a. snap action, comprising a pivoted actuating member, an overcenter spring ccnnecting said movable contact and said member, manual control means for moving said actuating member for shifting the line of action of said spring relative to the pivot point of said member to eiect opening or closing of said contact means, and a current-responsive trip element movable in response to predetermined conditions for shifting the position of said pivot point to change the line of action of said spring relative thereto to cause opening of said contact means irrespective 'of the position of said manual control means.

6. In a circuit breaker, contact means, means for moving said contact means to an open and to a closed circuit position with a snap action, comprising a movable contact actuating arm, a pivoted actuating member, an overcenter spring connecting said arm and said member, manual control means for moving said actuating member to shift the line of action of said spring relative to the pivot point of said member to effect opening or closing of said contact means, current-responsive trip means supporting said pivot point and being movable in response to predetermined conditions to change the line of action of said spring relative Vto said pivot point to open said contact means, and means for adjusting the trip characteristic of said currentresponsive trip means.

` 7. In a circuit breaker, contact means, means for moving said contact means to an open and to a closed circuit position with a snap action, comprising a movable contact actuating arm, a pivoted actuating member, an overcenter spring connecting said arm and said member, manual control means for moving said actuating member for shifting the line of action of said spring relative to the pivot point of said member to effect opening or closing of said contact means,4 and a current-responsive trip element supporting said pivot point, movable in response to predetermined conditions to shift the line of action of said spring relative to said pivot point to cause opening of said contact means, and adjusting means for dening the amount of movement of said element necessary to cause opening of said contact means.

8. In a circuit breaker, a stationary and a movable contact, means for moving said movable contact to an open and to a closed circuit position,

comprising a pivoted actuating member, an over.

center spring connecting said member and said movable contact, manual control means for moving said actuating member to shift the line of aisance action of said spring relative to the pivot point of said member to effect opening or closing of said contact means, a thermally responsive bimetallic trip element movable .in response to predetermined conditions for changing the position of said pivot point to shift the line of action of said spring relative thereto to eiect opening of said contact means, and adjusting means for defining the amount of movement of said bimetallic trip element necessary to cause opening of said contact means.

9. In a circuit breaker, contact means, means for moving said contact means to an open circit position or to a closed circuit position with a snap action, comprising a pivoted actuating member, an overcenter spring connecting said actuating member and said contact means, manual control means movable to an open or to a closed circuit position to shift the line of action of said spring relative to the pivot point of said actuating member to cause opening or closing of said contact means, and a bimetallic trip means supporting said pivot point, movable in response to predetermined conditions to change the line of action of said spring relative to said pivot point to cause opening of said contact means.

10. In a circuit breaker, contact means, means for moving said contact means to an open-circuit position or to a closed-circuit position with a snap action, comprising a pivoted actuating member, an overcenter springconnecting said member and said contact means, manual control means movable to an open or to a closed circuit position to shift the line of action of said spring relative to the pivot point of said member to cause opening or closing of said contact means, and a current-responsive trip means movable in response to predetermined conditions to shift the position of said pivot point relative to the line of action of said spring to cause opening of said contact means irrespective of the position ,of` said manual control means.

11. In a circuit breaker, contact means, means for moving said contact means to an open-circuit position or to a closed circuit position with a snap-action, comprising a pivoted actuating member, an overcenter spring connecting said actuating member and said contact means, manualv control means movable to an open or to a closed circuit position to shift the line of action of said spring relative to the pivot point of said actuating member to cause opening or closing of said contact means, and a current responsive bimetallic trip means connected in circuit with said contact means for supporting said pivot point, saidtrip means being movable in response to predetermined conditions to change the line of action of said spring relative to said pivot point to cause opening of said contact means, and adjusting means for defining the amount of movement of said trip element necessary to'cause opening of said contact means.

12. In a circuit interrupting device, the combination of a stationary contact, a movable contact, .means for moving said movable contact to an open or to a closed circuit position with a snap action comprising a pivoted contact carrying arm, a pivoted actuating member, anovercenter spring connecting said arm and saidy member, a manual control means for shifting the line of action of said spring relative to the pivot pointsof said arm and member to move said movable contact to the open or to the closed circuit position, a current responsive bimetallic trip element having a member secured thereto and projecting at an angle therefrom for supporting the pivot point of said actuating member, said trip element being adapted to be iiexed in response to predetermined values of current to move said pivot point of said actuating member in such a direction as to shift the line of action of said spring relative to both pivot points with increasing acceleration to effect movement of said movable contact to the open circuit position. f

13. In a circuit breaker a movable switch member, actuating means for moving the switch member to open and to closed position with a snap action including a pivoted actuating member and a trip element responsive to the currentiiowing in the circuit, said trip element carrying bearing means for pivotally supporting said actuating member at all times, said element being movable in responsev to predetermined current conditions to move the pivot of said member to cause opening movement of said switch member.

14. In a circuit breaker, a movable switch member, actuating means for moving the switch member to open and to closed position with a snap action including a pivoted yactuating member,A

manual means for moving the actuating member Ato open and to close the switch member, and

a trip element directly responsive to the current flowing in the circuit controlled by the breaker, said element having bearing means for pivotally supporting the actuating member and being movable in response 5to predetermined overload conditions to eect opening movement of the switch member.

15. In a circuit breaker, a movable switch member, actuating means therefor including an actuating membermovable to open -and tov closed position for moving said switch member to open and to closed positions, a movable operating member having opening and closing means for engaging said actuating member to move the same to open and to closed position in response to predetermined movements of said operating member, the path of movement of said operating member being so disposed relative to the path of movement of said actuating member that said actuating member is freeand clear of the closing means of the operating member in the closed circuit position of the breaker, and trip means for eilecting movement of said actuating member to open circuit position in response to predetermined conditions irrespective of the position in which the operating member is held.

16. In a circuit breaker, a movable switch member, actuating means therefor including a pivoted actuating member movable to open and to closed position to move said switch member to open and to closed position, a pivoted operating member having a closing projection for engaging and moving said actuating member to closed position when the operating member is moved to closed position and an opening projection for engaging and moving said actuating member to open position when the operating member is moved to open position, the pivot axis of said operating member being so disposed relative to the pivot axis of the actuating member that the closing projection of the operating member is clear of the path of movement of the actuating member in the closed circuit position of the breaker, and trip means operable in response to predetermined conditions to effect movement of the actuating member to open circuit position.

17. In a circuit breaker, a movable switch member, actuating means therefor including a pivoted actuating member, an overcenter spring connecting the actuating member to the switch member for moving the switch member to open and to closed position in response to predetermined movements o f the actuating member, manually operable means for moving the actuating member to effect opening and closing of the switch member, trip means for supporting the actuating member movable in response to predetermined conditions to effect movement of the actuating member to open position to cause opening movement of the switch member, and means for adjusting the line of action of the spring relative to the pivot axes oi the actuating member to vary the trip characteristic of the breaker.

18. In a circuit breaker, contact means, means for moving said contact means to an open circuit position or to a closed circuit position with a snap action, comprising a movable actuating member, a pivot point, a stressed member movable relative to said pivot point and connecting said actuating member and said contact means, said stressed member being movable to an open or to a closed circuit position to shift the line of action of said stressed member relative to said pivot point to cause opening or closing of said contact means, and a bimetallic trip means supporting said pivot point and movable in response to predetermined conditions to move said pivot point relative to the line of action of said stressed member to cause opening of said contact means.

19. In a circuit breaker, contact means, means for moving said contact means to an open circuit position or to a closed circuit position with f' a snap action, comprising a movable actuating member, a pivot point, a stressed member movable relative to said pivot point and connecting said actuating member and said contact means, said stressed member being movable by said actuating member to an open or to a closed circuit position to shift the line of action oi said stressed member relative to said pivot point to cause opening or closing of said contact means, a bimetallic trip means supporting said pivot point and movable in response to predetermined conditions for providing a force to move said pivot point relative to the line of action of said stressed member upon every movement of the bimetallic means an amount which varies with the amount of movement of the bimetallic means to cause opening of said contact means.

20. In a circuit breaker, contact means, means for moving said contact means to an open circuit position or to a closed circuit position with a snap action, comprising a movable actuating member, a pivot point, a stressed member movable relative to said pivot point and connecting said actuating member and said contact means, said stressed member being movable to an open or to a closed circuit position to shift the line of -action of said stressed member relative to said pivot point to cause opening or closing of said contact means, a bimetallic trip means supporting said pivot point and movable in response to predetermined conditions to move said pivot point relative to the line of action of said stressed member to cause opening of said contact means, said contact means when caused to move to open position in response to said blmetallic means remaining in open position after return of said bimetallic means to its original position, and a manually movable member operable to return said contact means to closed position.

21. In a circuit breaker, a movable contact member, actuating means for moving the contact member to open and to closed position with a snap action including an actuating member, a stressed member connected between said actuating member and said contact member, and a trip element responsive to the current owing in the circuit, said trip element carrying bearing means for pivotally supporting a part of said actuating means at all times, said trip element being movable in response to predetermined current conditions to move the pivot of said actuating means to cause opening movement of said contact member.

22. In a circuit breaker, a movable contact member, actuating means for moving the contact member to open and to closed position with a snap action including an actuating member, a stressed member connected between said actuating member and said contact member, said stressed member when in one position holding said contact member in open position and when in another position holding said contact member in closed position, and a trip element responsive to the current flowing in the circuit, said trip element carrying bearing means for pivotally supporting a part of said actuating means at all times, said trip element being movable in response to predetermined current conditions to move the pivot of said actuating means across the line of action of said stressed member when in its position holding said contact member in closed position to cause opening movement of said contact member.

23. In a circuit breaker, a movable contact member, actuating means for moving the contact member to open and to closed position with a snap action including an actuating member, a stressed member connected between said actuating member and said contact member, and a trip element responsive to the current flowing in the circuit, said trip element carrying bearing means for pivotally supporting a part of said actuating means at all times, said trip element being movable in response to predetermined current conditions to move the pivot of said actuating means to cause opening movement of said contact member, said contact member when caused to move to open position by movement of said trip element remaining in open position even though said trip element returns to its original position, and a manually engageable member for returning said contact member to closed position, said manually engageable member being incapable of holding said contact member in closed position upon movement of said trip element to cause opening movement of said contact member.

` HARLAN S. GANO. 

